Plug-switch.



G. K. MITCHELL.

2 SHEETS-SHEET 1.

Patented Oct. 6, 1914.

mm 0 mm k w 9 a 1 .M Mfl w G. K. MITCHELL.

PLUG SWITCH. APPLIGA'IIOII FILED DEC. 23, 1911.

Patented Oct. 6, W14

2 SHBETSSHEET 2.

3% J i w PLUG-SWITCH.

Specification of Letters Patent.

Application filial December 23, 1911. Serial No. 687/.285.

To aZZ whomit may concern:

Be it known that I, GUY K. Mrrciinnn, a citizen of the United States, residing in Baltimore and State of Maryland, have invented certain new and useful Inprovements in PlugSwitches, of which the following is a specification.

My invention relates to connecting devices for electric circuits, andniore' particularly to that class of such devices known as plug switches.

T he primary object of the invention is to provide a simple and practical plug switch capable of carrying the heavy currents used for driving large motors and the like. To this end, the invention contemplates the provision of improved switch members whereby the intimate contact necessary to good conductivity and etiicient operation is obtained.

Other features of my invention consist in providing means for insuring the'insertion oi the plug always in the same relative position, and means for preventing short-cirhandling of the plug.

While. my invention. is especially adapted for use in connection with threesphase or three wire systems, it is, in certain of its aspects, equally applicable totwo .wire, or multiple wire circuits.

1111 order that my invention :may be read-- ily understood, reference is had to theac-- specification, and illustrating, byway of examplcpthe invent-ion as embodied in a'plug sw it ch-ior 3-phase circuits. 1}

In these drawings: Figure view of the socket member of my improve its supporting member, the section being taken substantially on the line 5- 5. of Fig.

plug is in position, ment of the. plug;

I oimy complete switch as it. appears in use;

Fig. 8. a sectional elevation otithe cont. plete switch, showing a slightlyrmddifietl cuiting oi the live terminals by a carelesscoinpanying drawings, forming. part of this- 1 .is apla switch, withthe casing shown in sectioniy F 1g. 2 is a side QlEVELtlOH of the socket menion the line 2-2 of Fig. 1'; Fig.

is a side view thereof; Fig. 5 is a detail sec-- tionalview. of .one of the-contact blades and through $138111 Fig. 6 is a similar viewshowing the parts: in the relationwhich they assume when the and illustrating a irag- Fig. .7 is a front elevationouter end (iii-the contact blade,.an d a arrangement, and, Fig. 91s an. end view oi" the plug member shown in Fig. 8.

In the operation of certain classes oi and plants, as well as shops, andesp where individual motor drive for chines has been adopted, it is often desirable to move a machine from place to place and to be able to connect its motor with a source of currentsupply at any one of a plurality the ml,

of points. To meet these requiremen s in attic convenient and satisfactory manner, 1 proposeto install at various points throughout theshop or plant socket members or rec tacles constituting part of my improved receptacles with the mains.

Referring to the drawings. one of in y improved receptacles or socket members is clearly shown in l and 2. It comprises terial, which is surrounded by a casing2, provided with a door 8 hinged thereto at i. The base is provided with screw holes or the like 1, by means of which it may be attached to the wall or other suitable.support. The,

door is kept closed v at all times when the receptacle is not in use, so as to protect the contactdevices. Carried by theibase are a plurality of rigid supporting members,-three of such! members "being shown; in the drawing,

these members being arranged, in. this case, in the form of anequilateral triangle. of the members is preferably i.+shaped coinprises. an, upright portion 5 and a base portion 6, tothelatter. oi which is attached a binding post T.

Upon each of the supporting members just described is resiliently supported a contact blade 8, having an outwardly flaring upper endBE. This blade is so mounted as to A be capable.- of. pivotal movement relatima to the supporting member. The pref-erred niethodwoiv mounting consists, as clearly shown in Fim 5, in providingtheublade 8 with a plurality of pins or studs 9, 1G, rig- -.i dlysecured thereto, and adapted to protect 'ngs 11 and 12in the supporting member, such openings being con iderably larger than said pins, whereby Q2 oi the pins is permitted. As shown drawings, there is preferably prov-i single central .pin such as 9 adjac spaced pins, such. as-'10., adjacentthe .endthereoi. El e-p n 9 easits outs;

plug switches, and to connect each of such as abase lof slate or similar insulating ma? .215

' screw threaded and is provided with a nut larger than the opening 11 in the supporting member. A compression spring 14 surrounds the pin 9 between the blade 8 and the support, and a spring 15 surrounds each of the pins 10 between. the blade and the sup port; By this arrangement it will be seen that the plate 8 may have a pivotal movement relative to the support, such movement being possible by virtue of the large opening 11 through which the pin 9 works. It will also be observed that the plate 8 is resiliently supported adjacent its inner end by means of the springs 15, which springs normally serve to maintain the blade in the inclined position shown in Fig. 5 when the plug is withdrawn. The outward moyement of the inner end of the blade 8 is limited by the engagement of the pin 9 with the inner and outer edges of the opening 11. In order to positively and elliciently conduct current to the contact blade 8, a flexible conductor or pigtail 16 is provided, and is secured at one end to the blade 8 and at the other end to the binding post 7.

Each of the three blades, shown in Fig. 1, is constructed and connected in the manner just described. lVhile l have shown three of these contact blades, it is obvious that two could be employed to control a two-wire circuit, such blades being then arranged oppo site each other. lt is also equally obvious that four or more such blades could be employed, i] desired, the blades then being ar ranged along the sides of a corresponding polygon.

In installing my improved receptacles, I connect the binding post 7 to the conductors 26, leading to the mains, such conductors preferably being formed into a cable 25. This cable enters the casing through an openh1g2, a plurality of such openings being provided at the sides and ends of the box for the sake of convenience the particular opening employed depending upon the direction from which the cable is led.

In Figs. 3 and l I have shown an improved plug which is designed to cooperate with the socket member above described. This plug comprises a body portion 17 of insulating material such as wood, having prismatic faces to which are secured contact plates 18, as by means of screws 18 Three of such contact plates are shown in the drawing. By reference to Fig. 3 it will be noted that the contact plates 18 are considerably narrower than the width of the faces to which the plates are secured. This results in the insulating material projecting beyond the edges oi. the plates on both sides so as to etl'ectually separate them and prevent short circuit-mg. To the outer end of the contact plates 18 are secured connecting eyes 19, which are adapted to receive the terminals 22 of the conductors which form the cable 1,11aacc 21, such cable passing through the center of a hollow handle 20 which forms an axial continuation of the prismatic body 17. This hollow handle has openii'lgs therein through which the ends of the conductors pass, and is provided with a guard flange 21 adjacent such openings. It will be noted. that this flange is preferably quite wide, being of a diameter at least equal to that of the body 11', and thus serves to effectively prevent the lingers of the operator from coming into engagement with the contact plates or conductor ends.

lVhen the plug just described is inserted into the receptacle, each of the blades 8 assumes the position shown in Fig. 6, the spring 15 being placed under compression and the pins 9 and 10 assun'iing a position substantially at right angles to the supporting member 5. It will be seen that the blades 8 as constructed are thus self-alining, and that they are forced into close engagement with the contact plates throughout their entire length, thus producing a good conducting joint.

In three-phase work it is usually imma terial what angular position the plug occupies in regard to the contact blades, but in cases where it is necessary or desirable that the plug be always inserted in a definite relation I have provided the arrangement shown in Figs. 8 and 9. This consists preterably in providing an unsymn'ietrical projection, such as 27, on the end of the body 17 of the plug, and in forming a similarly shaped opening, such as 27, in the base 1. In the drawings I have illustrated the projection and opening as of T-shape, but other unsymmetrical shapes might be employed. In fact a mere pin set eccentrically into the plug would perform the same function. If preferred the projection may be secured to the base and the opening formed in the plug. Where the construction shown, however, is

employed it is desirable to space the base 1 I from the bottom 2 of the casing 2 by means of spacing blocks 1 as shown in Fig. 8.

In. order to take the strain oil of the re ceptacle and to insure the plug going in perfectly straight and true, I support the weight of the cable 21 by means of a hanger, which, as shown in Fig. 7, consists of a chain 28. This chain is attached to the cable adjacent the plug, by means of a clamping ring or wire 29, and is adapted to be engaged by a hook 30 preferably secured to the box or casing itself.

Not only does the provision of a casing serve to protect the contact blades and prevent external objects from coming into accidental engagement therewith, but it also serves to prevent short-circaitingof the corn tact blades due to careless handling of the plug. In other words, it makes it impossible to present the plug sidewis' to the receptacle nuance.

but compels the operator to pre ent it endwise, in which position, owing 0 the fact that the insulation projects beyond the contact plates, it is impossible to bridge two of th'eblades by means of any of the plates.

It will thus be seen. that I haveprovided an efficient plug switch having strong selfalining contact blades wel adapted for carrying the heavy currents met with inpraci tice, and it is thought that themany ad-- vantages of hy invention Willbe readily appreciated by those familiar with the re-- quirements of such apparatus.

What I claim is '1. In a plug switch, a socket member comprising a base, a plurality of rigid plates mounted in spaced relation on said-base and projecting at right anglestherefrom,

a contactblade supported each plate,

one end-of said blade being pivotally connected with-the plate at'a point i em'oteirom said base, and a compression spring nter- I posed between said blade and plate at a point between such base.

pivotal connection and 2. A plug switch compi'ising a socket membenhaving contact blades, a rigid support to which each, of said blades is resiliently secured, such securing means com-- pnsin'g a pair of PIILS CaI'IIQd by each of said blades and located one adjacent each .end. thereof, said support having openings through which such pins loosely, extend, one

of said pins having ahead incapable of passing throughthe associated opening, and acoll spring surroundingeach in said pins 

